Disconnect Switch: Learn the Purpose, Cost, and Lead Time to Procure

Purpose of disconnect switch

Disconnect switches establish isolation points to enable equipment maintenance. They are installed on both sides of the circuit breaker, high-side of the transformer, and on the line exit.

Location of disconnect switches inside a substation

Switches cannot and should not be used to interrupt load current or fault current. A switch operation takes place after the circuit is de-energized.

Cost of disconnect switch

A switch can be designed in numerous ways – vertical break, center break, side break, double side break, pantograph, etc. View some of them here. The prices below reflect your typical vertical break configuration.

365kV 3000A motor operated disconnect switch: ~$50,000
138kV 2000A motor operated disconnect switch: ~$20,000

Lead time to procure disconnect switch

~22 weeks for a high voltage switch.

Information on cost and lead time is for your general knowledge only. Contact vendor with your equipment specifications for actual figures.

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Disconnect Switch: Learn the Purpose, Cost, and Lead Time to Procure 1

Substation Major Equipment

It’s only stupid-simple, let’s begin.

What’s the purpose of a conventional power transformer?

Transform power, voltage, and current

Transform voltage and current

Transform voltage only

Which combination of devices would you use to implement power line carrier?

Wavetrap, capacitor coupled voltage transformer, and line tuner

Wave trap, capacitor voltage transformer and line tuner

Wave trap and line tuner

In a distribution substation, the available ground-fault current on the low side of the step-down transformer is excessive, over-dutying the switching equipment. What is your cost-effective solution to reducing the fault current?

Buy new transformer with higher impedance (%Z)

Add inductor in the transformer neutral

Add current limiting fuses in series on the switchgear

Add series inductors

You are building an interconnect station, tying wind farm generation to the power grid. At the substation, the sources are tied through a tie-breaker. Which device would you install to make sure the sources are synchronized?

Voltage transformer

Current transformer

Ideal transformer

Power transformer

An industrial facility is plagued with voltage flicker (due to harmonics) and poor power factor at the service entrance. Which device would you install to fix both issues?

Voltage regulator

Harmonic filter bank

Install capacitor bank

A transformer develops an internal fault. Which device would you install on the transformer high-side to interrupt fault current?

Disconnect switch

Either a breaker or a circuit switcher

Circuit switcher

Circuit breaker

For which event should a surge arrester operate? Check all that apply.

Phase-to-ground short-circuit

Lightning strike

Temporary overvoltage

Switching surge

Your score is

The average score is 41%